Sony NEX6, NEX7 and A7 Comparison (low-light)

December 07, 2013  •  1 Comment

It's been a very long time since my last post, but I thought I'd ressurect the blog with a post about NEX camera and the new Sony A7.  Particularly whether using E-mount lenses on the A7 in low light brings any benefit over using the same lenses on the NEX6.

I've been using the Sony NEX system since 2011.  It all started when I wanted a compact alternative to a DSLR to use on a long night-walk, and the NEX-5 had an APS-C sensor and a decent price (at the point I bought mine it had just been replaced by the NEX-5N).  The results are here, and I loved using that camera on the walk and as a general walkaround camera.

A year or so later, I finally upgraded to the top-of-the-range NEX 7 with it's 24MP APS-C sensor, and loved the detail you could get from that sensor in good light.  There were a couple of problems though.  The lens range had grown to some extent by this point, but there still wasn't the choice that you could get for the established DSLRs.  And when you turned down the light and pumped up the ISO, the noise started in abundance.

Add another year, and I acquired a new NEX - the NEX6.  The pixel count dropped from 24 to 16MP with the same size APS-C sensor and this definitely improved the low light performance.  I had got the 35/1.8 by this time and really loved the look of the images produced, but I did find 35mm on an APS-C sensor (about 50mm full-frame equivalent) a little long.  And I refused to pay 800+GBP for the Zeiss 24/1.8!

While the user interface of the NEX6 was improved over the NEX7 and NEX5 it was still irritating (ask any NEX user!) and there were some basic usability issues with the camera.  For example, I use Auto-ISO quite a bit and on the NEX series camera this will drop the shutter speed to a minimum 1/60s as soon as the light drops - there's no control over this.  While this is enough to compensate for any hand-holding vibration on sub 50mm lenses, it just isn't fast enough to get rid of blur on subjects like moving children!

So, roll on the full-frame A7.  I don't have a lot of time at the moment so I'll go into more detail in a post soon... but I love the A7.  (Almost) all the irritations with the NEX system seem to be gone - the menu system is massively improved, you can use Auto ISO in Manual mode, there's lots more controlability over various aspects that were locked down in the NEX cameras.  And it just feels really good without being significantly bigger.  And the IQ... well, gut feeling and with a bit of new-gear love, I'd say it comes pretty damn close to my 5D3/6D/D800 for IQ - so much so that it makes no difference.  The only issue still remaining is the lens choice, and right now it's far worse than even the E-mount choice (as I write this, there are 2 lenses available - the FE28-70/3.5-5.6 kit lens and the Zeiss FE35/2.8).

So there's a bit of an intro.  Now to the point of this post...

Quality Comparisons

I did a very basic comparison shot of the same subject under the same light with the NEX6, NEX7 and A7, cropped the same area of the image and exported with the same settings in Lightroom.  This is an attempt to be a real-world test rather than anything too analytical, so it's not under typical lab conditions.  As I explain below, some cameras get some significant noise-reduction benefits too as the final image is scaled to the same size for web viewing.

The camera settings for all cameras were as follows:

  • NEX6: 35mm on the E16-50OSS at f/5.6
  • NEX7: 35mm on the E35/1.8 at f/5.6
  • A7: about 50mm on the FE28-70 at f/5.6 to give the same field-of-view as 35mm on the APS-C cameras
  • also A7: 35mm with the 35/1.8 in APS-C crop mode (giving total image size of 10MP)

Here are the images with a bit of discussion below

ISO6400

NEX6

NEX6_6400

NEX7

NEX7_6400NEX7_6400

A7 Full-Frame (53mm)

A7_6400_FFA7_6400_FF

A7 (35mm E-mount lens, crop mode - 10 megapixel)

A7_6400_CropA7_6400_Crop

ISO 12800

NEX6

NEX6_12800NEX6_12800

NEX7

NEX7_12800NEX7_12800

A7 Full-Frame (53mm)

A7_12800_FFA7_12800_FF

A7 (35mm E-mount lens, crop mode - 10 megapixel)

A7_12800_CropA7_12800_Crop

Discussion

The first thing to point out here is that this is not a level playing field from a per-pixel quality point of view.  That's not the point of this exercise.  What I'm trying to look at is what sort of quality you can end up with if you have a scene in front of you and you want to capture it in a certain way with any of the tested cameras.

All the images above are scaled to 940px across (view them full-size to see them at this resolution), but the source image was from many more pixels:

NEX6 - scaled to about 42%

NEX7 - scaled to about 34%

A7 (FF) - scaled to about 34%

A7 (crop) - scaled to about 45%

When the initial image is made smaller - as long as the downscaling is intelligent (as it will be in Lightroom) - the noise-per-pixel of the output image will be reduced.  So the noise in the NEX7 and A7 (FF) images will have been reduced most in the downscaling for output, and least in the A7 (crop).

My Opinion

Well, at ISO 6400 and 12800, I think it's plain to see that the NEX7 doesn't perform that well.  It's had the most help (noise reduction from downscaling) and still looks noisiest.

The full-frame A7 looks the best by a considerable amount - the full-frame 12800 ISO shots show a great control of noise and should give an idea of the performance of this camera.

Cropped A7 shots compared to NEX-6 shots take a bit more thinking about.  Judging from the images above, I'd say the cropped A7 does take the prize but only marginally.  This means that each pixel on the A7 is significantly better in lower light than the NEX6, but the extra 6MP of the NEX6 (16MP compared to the A7's cropped 10MP) do give the final output image a boost in quality when you downscale as you will in most screen and print situations.

Conclusion

The question I was trying to answer with this post is whether the cropped mode on the A7 brings any benefit over using the same lens on the NEX6 (particularly in low light), and I think it does... but only fractionally.  However, stick a full frame (FE) lens on the A7, and you'll blow away any NEX camera.

So, don't buy an A7 if you only have E-mount lenses, but if you're planning on stumping up the notes for FE lenses then you won't be disappointed.


Comments

1.webcamera(non-registered)
When you want answer about NEX6 or A7

A : say

I thought I had it all figured out between the nex 6 and 7, but with the new Alpha 7 and 7R coming out early next year I have no idea anymore. I realize that since they are available yet, this is not an easy question, but was hoping that just going by the info out there someone might have an opinion?

What I'm looking for is something decent to catch shots of siberian huskies, which run like the wind :) I would also be taking kids pics and vacation pics too. I had it all narrowed down to the nex 6 over the 7. Now I'm wondering if maybe the new A7 will be a good choice?


B : say

What are your reasons for considering the Nex 6 or 7? What more do you think the 7 or 7R will give you?

Generally, the dSLR cameras, like a Canon Rebel, will focus faster, if that is a major consideration. And picture quality will be similar to a NEX 7.

There's no doubt the new 7 and 7R are going to have great image quality. Important if you are making very large prints, but most system cameras today produce high quality images. And the selection of Sony lenses for the 7 is going to be limited for a while, and expensive. And telephoto lenses are not going to be small.

More : http://webcamerawebcamera.com/detail.php?id_detail=109
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